Hitherto, an air-conditioning apparatus that conveys cooling energy or heating energy to a conditioned space, such as an indoor room, by causing a refrigerant to circulate between an outdoor unit serving as a heat source unit disposed outdoors and an indoor unit disposed indoors so as to perform cooling operation or heating operation is applied to a multi-air-conditioning apparatus for a building (for example, see Patent Literature 1). As a refrigerant used in such an air-conditioning apparatus, an HFC (hydrofluorocarbon) based refrigerant is commonly used. Moreover, in recent years, natural refrigerant, such as carbon dioxide (CO2), has also been used.
There are also other air-conditioning apparatuses with different configurations, one representative example of which being a chiller system. Such an air-conditioning apparatus performs cooling operation or heating operation by generating cooling energy or heating energy in a heat source unit disposed outdoors, transferring the cooling energy or the heating energy to a heat medium, such as water or antifreeze, at a heat exchanger disposed in the outdoor unit, and conveying the heat medium to a fan coil unit or a panel heater serving as an indoor unit disposed in the conditioned space (for example, see Patent Literature 2). Furthermore, a so-called waste heat recovery chiller in which the heat source unit is connected to four water pipings for supplying cooling energy or heating energy is also known.